Method of treating oil wells



Patented May 6, 1941 Z,241,254 METHOD OF TREATING 01L WELLS Allen D.Garrison, Houston, Tex asslgnor to The Texas Company, New York, N. Y., acorporation of Delaware No Drawing. Application July 6, 1938, Serial No.217,733

, sulfonate within the sand to form the said water 9 Claims.

This invention relates to the treatment of an oil well, and moreparticularly to the chemical treatment of the sand adjacent a producingwell in order to render the sand preferentially wettable by oil tothereby increase the proportion of oil and decrease the proportion ofwater produced by that well.

It is recognized that ordinary sand is more easily wet by water than byoil. It is further recognized that oil producing sands are predominantlywater-wet. When the pore spaces of an oil producing sand contain bothwater and oil the fact that the sand surfaces are water-wet will causethe water to occupy the smaller capillaries and crevices to theexclusion of the oil, thereby limiting the flow of the oil to the largercapillaries only, this flow of oil through these capillaries beingretarded because the pore spaces of the capillaries are substantiallyreduced in cross-section by the presence of the relatively immobilewater film on the sand grains. The oil flow into and through the smallercapillaries and crevices is opposed by the interfacial tension betweenthe oil and the water. My invention resides in a method of causing oilto flow through all of the capillaries and crevices of an oil producingsand by removing the water film from the walls of the capillaries andcrevices, and rendering the surfaces oil-wettable. In this manner, theflow of water into the Well is retarded by the same force whichobstructs the flow of oil through the average water-wet oil producingsand.

In Patent No. 2,024,119, issued to William V.

Vietti and Allen D Garrison, there is disclosed and claimed a method oftreating a producing sand of this character which is wet with water, bythe depositing of a water and oil insoluble precipitate on the sandgrains, which precipitate is of such character that it does not fill orblock the pore space of the sand and is preferentially wettable by oilso that the sand becomes wet with oil, whereby the proportion of oilproduced by the well is increased while the proportion of water soproduced is decreased. In accordance with the method of said patent, awater solution of a water soluble alkali metal salt of a sulfonated fat,fatty acid or oil is introduced into the well and into the sand adjacentthe well, and this solution either reacted with the calcium andmagnesium salts of the brine naturally occurring in the well, or elsereacted with a subsequently introduced water solution of a solublealkaline earth or heavy metal salt, to cause precipitation of analkaline earth or heavy metal and oil insoluble film coating upon thesand grains. 7

The present invention constitutes an improvement over the method of saidpatent, and involves additional treatment of the producing sandfollowing the deposition of the water and oil insoluble film coatingupon the sand grains to substantially completely remove water from thepore space of the treated sand adjacent the well bore.

In accordance with the present invention, the producing sand is firsttreated to deposit a water and oil insoluble film coating upon the sandgrains, which coating is preferentially wettable by oil. The treatedsand is then dehydrated to remove water from the pore space thereof, asby introducing into the well under pressure a dehydrated gas to causeevaporation of the water or to drive the water farther back into theformation. Thereafter, a charge of oil is forced into the well and intothe treated sand; so as to insure that the sand is wet with oil and thepore space thereof substantially free from water, prior to theproduction of oil from the well.

The initial coating of the sand grains with a thin adhering film of awater and oil insoluble precipitate which is preferentially wettable byoil may be accomplished in the manner disclosed in the above mentionedPatent No, 2,024,119. As set forth therein, there is forced into thewell and into the sand adjacent the well, a solution of a precipitatablecompound of the preferential wetting character described. This isfollowed by a solution of a compound which is active to react with thefirst mentioned compound to produce the desired precipitate when thesetwo solutions are brought into contact with each other within theproducing sand being treated, whereby the precipitate so produced isefiectively distributed and deposited throughout the treated sand zoneadjacent the well bore, The Procedure described above may be repeatedone or more times, so asto secure the desired effective deposit andcoating of the sand grains throughout the water-wet sand.

Suitable materials which possess the preferential wetting propertyinclude various water and oil insoluble salts of sulfonated oils, fatsor fatty acids. For example, the alkaline earth and heavy metal salts,including those of calcium, barium, iron, manganese, zinc, tin, lead,and the like, of sulfonated oils, fats or fatty acids may be employed.Natural fats, such as tallow, olein,

stearin, and the like. which have been sulfonated by treatment withsulfuric acid, are suitable. Likewise, sulfonated fatty acids formed bysulfonating stearic, pahnitic, oleic and the like, are included. A verysatisfactory and comparatively cheap material, which is a by-product ofthe petroleum industry, is the sulfonic sludge acid derived from thetreatment of petroleum oil with sulfuric acid, and termed herein apetroleum oil sulfonate. These various materials may conveniently beused in the form of their alkali metal whereby a water solution of thesoluble salt' may first be forced into the bore of the well and into thesand immediately surrounding the well. Then a water solution of awater-soluble salt of calcium, barium, or other alkaline earth or heavymetal, such as a chloride or ,iiitrate, is forced into the well and intothe sand to react with the first mentioned solution to produce aprecipitate of the water and oil insoluble 5 metal salt of thesulfonated oil, fat or fatty acid upon the sand grains.

If suilicient brine carrying naturally-occurring calcium and magnesiumcompounds is present in the producing sand being treated, theintroduction of the initial water solution of alkali metal sulfonate, soas to react insitu with the calcium and magnesium compounds of thebrine, may be sufficient to produce the desired coating.

In addition'to the materials specified above for producing the oilwettable coating, other substances can be employed, such as the metallicsulfides of my co-pending application Serial No. 212,975, filed June 10,1938, including the sulfides of heavy metals which do not hydrolyze inslightly acid water such, for example, as sulfide of lead, copper,cadmium, cobalt, iron, mercury, molybdenum, nickel, tin, silver, zinc,arsenic, antimony, and the like. This coating is conveniently formed byintroducing into the well a mineral oil solution of a heavy metalcompound which is soluble in the oil, and following this by theintroduction of a mineral oil solution of a sulfide compound whichreacts within the producing sand with the, heavy metal compound toproduce a precipitate of a heavy metal sulfide. Various heavy metalsoaps which are sufiiciently oil-soluble to be employed in this mannerare satisfactory for this p pose, such as heavy metal salts of oleic,stearic, palmitic and other fatty acids as well as the heavy metal saltsof naphthenic acids.

tions can be employed as the solvent, such as kerosene, naphtha, gasoil, lubricating oil or crude oil. Following the introduction of the oilsolution of the heavy metal soap, there is then charged into the well anoil solution of an oilsoluble sulfide ,compound such as hydrogensulfide. The same mineral oil fractions as specified above may beemployed as solvents for the sulfide compound used.

In addition to the above compounds for producing the oil wettable filmcoating, there may be employed a film coating of a water and oilinsoluble bitumen of my co-pending application Serial No. 212,976, filedJune 10, 1938, such as may be obtained from a petroleum or coal tarpitch, asphalt, natural asphalt and the like. A very satisfactorymaterial for this purpose is a modified asphalt produced by sulfurizingasphalt at high temperatures, or by highly oxidizing asphalt by airblowing for extended periods of time and at temperatures to produce aresultant asphaltic material which is substantially insoluble in crudeoil as well as in water. A

Various mineral oil fracsatisfactory and cheap starting material for theproduction of this water and oil insoluble asphalt is a crackedpetroleum residue such as a cycle fuel oil or a heavy pitch derived fromcracking operations. The bituminous or asphaltic materials of this typemay be applied to the sand in the form of an extract of the same in asuitable non-aqueous organic solvent. Various aromatic solvents of thecharacter of benzol, toluol, xylene, light coal tar oil and the like maybe employed. Likewise, chlorinated aromatic solvents such aschlorbenzene and nitrated aromatic solvents such as nitrobenzene may beused. Also, certain chlorinated aliphatic solvents such as carbon:tetrachloride, or other solvents of high solvent power such as carbondisulfide may be used. These solvents will dissolve a substantialproportion of the modified asphaltic material which is insoluble incrude petroleum oil, and consequently will be precipitated upon contactby and dilution with oil in the pore space of the sand.

Irrespective of the method and the compounds employed to produce thedesired film coating upon the sand grains, the pore space of the sandmay still contain a substantial proportion of water, where the filmcoating is not preceded by a dehydrating treatment as disclosed andclaimed in my co-pending applications Serial No, 212,974, filed June 10,1938, and Serial No. 212,976, filed June 10, 1938. Particularly in thecase where the desired film coating is formed by introducing watersolutions of the compounds which react within the pore space of the sandto produce the desired precipitate, will substantial quantities of waterbe present therein. But even in the case where oil or aromatic solutionsare employed, it is found that these are ineffective to completely flushthe water from the treated sand zone. In accordance with the presentinvention, the film coating step as described above is followed by adehydrating treatment which is effective to substantially completelyremove remaining water from the pore space of the treated sand. This maybe conveniently accomplished by introduca gas under pressure, so thatthrough the pore space of the producing sand adjacent the well to takeup and remove moisture therefrom, and to force unevaporated waterfarther out into the formation. Any suitable gas may be employed forthis purpose, such as air, flue gas, natural gas, methane and the like.Preferably, this gas is compressed, cooled and dehydrated before it isintroduced into the well. Other methods of dehydration may be employed,such as by lowering a heated body or electrical heater to the wellopposite the producing sand which has been treated, either with orwithout the application of gas under pressure so as to pass over theheated body and thence into the producing sand.

Following the dehydration of the treated sand, which will leave theproducing zone immediately around the well bore with a dried coating ofthe preferentially oil-wettable material, there is introduced into thewell a flushing oil so as to insure wetting of the treated sand with oiland filling of the pore space thereof with oil substantially free fromwater. Any suitable crude oil or mineral oil fraction can be employedfor this purpose. Preferably there is used a crude oil carrying insuspension a hydrophobic colloidal material, such as very finely dividedasphalt, tar acids, graphite, coke particles, pitchy residues and thelike. Such hydrophobic colloidal material will tend to deposit upon thesand grains in the absence of water, giving a wider and more uniformapplication of the film coating than may be obtained by the initialtreatment in the presence of water. The net result is that the producingsand adjacent the well bore is effectively wetted by oil in thesubstantially complete absence of water, and such sand will offerincreased resistance to the subsequent encroachment of water into thattreated zone. The well is then ready to be placed on production, withthe result that the proportion of oil produced is materially increased,while the production of water from that well is greatly reduced, if notsubstantially completely prevented, at least for an appreciable timefollowing the treatment.

As a further modification, the gas used to dehydrate the sand may haveincorporated therein a substantial proportion of hydrogen sulfide, whichis found to assist in waterproofing the pores of the treated zone. V

Obviously many modifications and variations of the invention, ashereinbefore set forth, may be made without departing from the spiritand scope thereof, and therefore only such limitations should be imposedas are indicated in the appended claims.

I claim: 1. In the method of treating an oil well to convert a water-wetproducing sand to one which is preferentially wettable by oil, the stepswhich comprise coating the sand grains of the said producing sandadjacent the bore of the well with a film coating which ispreferentially wettable byoil without blocking the said sand, and thendehydrating the coated sand to substantially completely remove waterfrom the pore space of the treated sand adjacent the well bore.

2. The method of treating an oil well to convert a water-wet producingsand to one which is preferentially wettable by oil, which comprisescoating the sand grains with a film coating which is preferentiallywettable by oil, then dehydrating the coated sand, and finally flushingthe coated and dehydrated sand with oil.

3. In the method of treating an oil well to convert a water-wetproducing sand to one which is preferentially wettable by oil, the stepswhich comprise coating the sand grains of the said producing sandadjacent the bore of the well with a film coating which ispreferentially wettable by oil without blocking the said sand, and thenblowing the coated sand with a gas to substantially completely evaporatemoisture therefrom and force remaining water farther out into theformation.

preferentially wettable by oil, which comprises coating the sand grainswith a film coating which is preferentially wettable by oil, thendehydrating the coated sand, and finally flushing the coated anddehydrated sand with oil carrying a hydrophobic colloid which willdeposit upon the coated sand in the absence of water.

6. In the method of treating an oil well to convert a water-wetproducing sand to one whichv is preferentially wettable by oil,involving the coating of the sand grains with films which arepreferentially wettable by oil, the steps of compressing, cooling anddehydrating a gas, and then forcing the cooled and dehydrated gas intothe well and into the said sand to substantially completely remove waterfrom the pore space of the said sand adjacent the bore of the well.

7. In the method of treating an oil well to convert a water-wetproducing sand to one which is preferentially wettable by oil, involvingthe coating of the sand grains with films which are preferentiallywettable by oil. the step of introducing into the well and into the saidsand a gas containing hydrogen sulfide to remove water therefrom and towaterproof the dried sand.

8. In the method of treating an oil well to convert a water-wetproducing sand to one which is preferentially wettable by oil, the stepsof blowing the sand with a gas to evaporate water therefrom and forceremaining water farther out into the formation, and then flushing thedehydrated sand with oil carrying a hydrophobic colloidal material todeposit the said colloidal material upon the sand grains and render thempreferentially wettable by oil.

9. In the method of treating an oil well to convert a water-wetproducing sand to one which is preferentially wettable by oil. the stepsof dehydrating the sand, and then flushing the dehydrated sand with oilcarrying a hydrophobic colloidal material to deposit the said colloidalmaterial upon the sand grains and render them preferentially wettable byoil.

ALLEN D. GARRISON.

